Project Summary As the second leading cause of death in the US, cancer has a considerable impact of cancer on society, and a better understanding into the mechanisms of disease and potential therapeutics is needed. One proposed therapeutic target is the sumoylation pathway, which involves the post-translational modifications of proteins by the Small Ubiquitin-like Modifier (SUMO; sumoylation) and requires the SUMO-activating enzyme (SAE1/SAE2), the SUMO-conjugating enzyme (Ubc9), one of the few identified SUMO-E3 ligases, and SUMO proteases (SENPs). The end result of sumoylation is the regulation of protein function in numerous ways. Sumoylation processes are dysregulated in many cancers, and we recently documented that sumoylation processes are up-regulated in lymphoma tissues in the presence of Latent Membrane Protein-1 (LMP1), the principal oncoprotein of Epstein-Barr virus (EBV). However, additional insight into how LMP1-modulated sumoylation processes contribute to the oncogenic nature of LMP1 is warranted. As the principal viral oncoprotein of EBV, LMP1 is responsible for the sustained cellular proliferation, increased cell survival, increased cell invasion and metastasis due to its ability to constitutively activate multiple signal transduction pathways via its three cytoplasmic C-terminal activating regions (CTARs). Our work suggests that the three CTARs allow LMP1 to manipulate distinct steps of the sumoylation process. LMP1 activates the sumo promoters, hijacks Ubc9, and represses the activity of SUMO proteases, all of which results in the accumulation of sumoylated proteins. The end result is the maintenance of latency, modulation of innate immune responses, and regulation of oncogenesis. These data demonstrate a critical role for LMP1- mediated regulation of sumoylation processes and emphasize the need to further identify how LMP1 manipulates the sumoylation machinery during latent EBV infection. Preliminary data suggest that LMP1 also interacts with SAE1, SAE2, and the SUMO E3 ligase Ran Binding Protein-2 (RanBP2), so we hypothesize that LMP1 manipulates each step of the sumoylation process thereby modulating the oncogenic potential of LMP1. This hypothesis will be tested in three aims that will 1) determine the effect of LMP1 on SAE1 and SAE2; 2) determine the effect of LMP1 on RanBP2; and 3) further elucidate how LMP1 manipulates the SUMO protease SENP2. This project will focus on three distinct steps of the sumoylation process (activation of SUMO, SUMO ligation, and de-sumoylation). During the timeline of the proposed project, at least 15 undergraduate, graduate, and medical students will be exposed to basic medical research, gaining hands on experience in the laboratory, collecting data and learning to analyze and present the research findings. The proposed research will enhance research and education at MUSM and expose numerous students to careers in the medical field.